LEWIS NUMBER AND VAPORIZATION EFFECTS IN SPRAY DIFFUSION FLAMES

A recently proposed model of a Burke-Schumann spray diffusion flame is extended to permit preferential diffusional effects via relaxation of the unity Lewis number assumption. In this way the interaction between transport and vaporization effects in such flames may be examined. Situations in which the gaseous fuel and oxidant Lewis numbers are either equal or different from each other are treated. In addition, droplets that survive the intense homogeneous reaction zone are assumed to burn beyond the flame front, either individually or in clusters (assuming that the flame is of the overventilated type). Computed results based on the analytic solutions reveal the manner in which the spray flame characteristics are sensitive to coupled gaseous- and spray-related parameters. For example, with a fixed fuel Lewis number, it was found that the flame height may be altered by changing the oxidant Lewis number. This effect may actually be enhanced by the presence of a spray of droplets under suitable operating conditions.